CHANGES IN ETHYLENE AND POLYAMINES IN RELATION TO MESSENGER-RNA LEVELS OF THE LARGE AND SMALL SUBUNITS OF RIBULOSE-BISPHOSPHATE CARBOXYLASEOXYGENASE IN OZONE-STRESSED POTATO FOLIAGE

Potato plants (Solanum tuberosum L. cv 'Norland') were subjected to ac ute and chronic exposures of ozone (O3). Periodically following or dur ing the exposures, foliage of different physiological ages were sample d for tissue analysis. Measurement of the following parameters were in cluded: ethylene, 1-aminocyclopropane-l-carboxylic acid (ACC), N-malon yl 1-aminocyclopropane-1-carboxylic acid (MACC), and ACC oxidase activ ity, putrescine, spermidine, and spermine levels, and ornithine decarb oxylase (ODC) activity, and levels of mRNA transcripts for the large a nd small subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase ( Rubisco) (rbcL and rbcS, respectively). Ozone increased emission of et hylene and the concentration and activity of all associated metabolite s and enzymes. Putrescine titre increased in response to 03 as did ODC activity. Some increases in spermidine were also detected. Ozone decr eased the levels of mRNA for rbcL and rbcS, with the latter transcript exhibiting greater sensitivity. After acute exposures were terminated , the rbcL and rbcS transcript in younger leaves returned to levels of nonstressed plants; effects were less likely to be reversed in older tissue. The potential relationship between the changes in rbcL and rbc S and ethylene and polyamines are discussed in the context Of 03 induc tion of accelerated senescence.